Method of chromatographic analysis using siloxy carboranyl partitioning phases

ABSTRACT

Vapor phase chromatography wherein a siloxy carboranyl liquid partitioning phase having recurring structural units of the following formula is used:   WHERE EACH R and R&#39;&#39; substituent is an independently selected alkyl group of one to eight carbon atoms or aryl group of up to 10 carbon atoms and x is 1 to 5. These siloxy carboranyl partitioning phases are particularly useful at high temperatures.

United States Patent Finch et al.

I 54] METHOD OF CHROMATOGRAPHIC ANALYSIS USING SILOXY CARBORANYLPARTITIONING PHASES I 72] Inventors: Richard w. Finch, Northford;Willard Alan Nichols, Madison, both of Conn.

[ 73] Assignee: Olin Corporation (22] Filed: Aug. 10,1970

[2]) Appl. No.: 62,624

Related U.S. Application Data [63] Continuation-impart of Ser. No.879,696, Nov. 25,

1969, abandoned.

[52] U.S. Cl ..55/67 [5i] lnt.Cl ..B01d 15/08 [58] Field ofSearch..2l0/3l, 198; 55/67, 197, 386; 73/23.]

[56] References Cited UNITED STATES PATENTS 3,263,401 8/1966" Supina..55/67 RESPONSE MILL IVOL rs ZEMPmArt/RE "C [1 1 3,660,966 [45 May9,1972

3,464,183 9/1969 Gordon ..55/67 Primary Examiner-J. L. De CesareAttorney-Eugene Zagarella, .lr., Gordon D. Byrkit, Donald F. Clements,F. A. lskander and Thomas P. O'Day [5 7] ABSTRACT Vapor phasechromatography wherein a siloxy carboranyl liquid partitioning phasehaving recurring structural units of the following formula is used:

8 Claims, 4 Drawing Figures CHROMATOGRAPH/C Rama/s5 VERSUS TEMPERATUREME77-IVL SILICONE .s/Loxr CAREORANE PATENTEDMAY 9 I972 660 966 sum u BF4 CHROMATOGRAPH/C ANALYSIS OF REACT/0N INTERMEDIATES METHYL SILICONE oTFMPERAfL/RE C S/LOXV CARBORANE EMPERATURE C INVENTORS' RICHARD W F/NCHFIG-4 WILLARD ALAN NICHOLS BY W y fl k AGENT METHOD OF CHROMATOGRAPH ICANALYSIS USING SILOXY CARBORANYL PARTITIONING PHASES This application isa continuation-in-part of copending application U.S. Ser. No. 879,696filed Nov. 25, 1969, and now abaondoned.

This invention relates to the use of siloxy carboranyl liquidpartitioning phases in vapor phase chromatography.

Vapor phase chromatography (VPC) is an extremely versatile analyticaltechnique which is used to separate components for quantitative andqualitative analysis. It is a nondestructive technique which utilizesmicro amounts of sample and can perform part per billion analyses in amatter of minutes. Because of its versatility of technique, ease ofoperation and maintenance and a relatively moderate purchase price ofequipment and material, VPC has gathered wide acceptance. Continueddevelopment programs directed toward improving VPC have resulted in awide variety of available detectors, intricate temperature programingmodes, a multitude of partitioning phases and new data reductionsystems.

' However, despite its wide use and continued development, there hasbeen little improvement in the area of usable temperature limit. Sincemethyl silicon gum (General Electric SE-30) was introduced as achromatographic phase, it has been generally accepted as the hightemperature phase and its upper temperature limit of 350 C. hasgenerally been considered as the usable limit for VPC. This isparticularly disadvantageous because high boiling components such aspolymers, reaction residues, metallo-organics, petroleum byproducts,pesticides, biochemical materials, .many inorganic materials, etc., willnot elute from the column and unfortunately, this area of high boilersoften constitutes a major portion ofthe sample.

This invention relates to VPC using a siloxy carboranyl liquidpartitioning phase which results in a high temperature limit andthereby, appreciably extends the usable range of VPC. This isparticularly advantageous because many new chemical areas may thereby besusceptible to analysis by this technique. In addition, the lifetime ofthe chromatographic columns and-detectors may be increased and postseparation analyses such as trapping or direct mass spectrometercoupling, will not be subject to phase contamination.

Basically, they chromatographic process is conducted in a VPC columnwherein a randomly packed network of inert solid support material isheld. The support material is coated with a partitioning phase and aninert carrier gas transports a volatile mixture through the column andinto contact with the partitioning phase. The volatiles are firstadsorbed and then desorbed by the phase and if this rate is differentfor the various components of the mixture, they become separated and aredetected as they exit from the column.

One of the main problems of high temperature chromatography is findingpartitioning phases capable of withstanding high temperatures. The hightemperatures affect the partitioning phase in three ways: 1) thermaldecomposition, (2) interaction with components of samples and (3) simplevaporization or carrying away by the carrier gas. The latter effectresults in eventual shortening of retention times, broadening of peaksand loss of resolution and changes in relative retention times ofdifferent peaks in the sample. In addition, the detectors can bedesensitized or destroyed and if the phase does get past the detectors,any isolation of the original sample components will be contaminated byphase.

This invention relates to the use of a liquid partitioning phase in apacked column wherein the previously discussed problems concerning theuse of partitioning phases unsuitable for high temperature operation areeliminated or minimized.

More particularly, this invention involves the use of a siloxycarboranyl liquid partition phase having recurring structural units ofthe formula:

R I l where each R and R is an independently selected alkyl group of oneto eight carbon atoms or aryl hydrocarbon group of up to IO-carbon atomsand x is l to SLThus, for example the R and R substituent may be methyl,ethyl, butyl, octyl, phenyl, tolyl, xylyl or naphthyl.

Basically, the compounds used in this invention are prepared by reactingan alkoxy substituted neocarborane with a halogen containingsilane orsiloxane or by reacting a dialkoxy silane with organosiloxanylcarborane. More particularly, the compounds used in this invention maybe prepared by the methods as disclosed in U.S. Pat. Nos. 3,388,091,

3,388,092 and 3,388,093.

Generally the compounds used in this invention have molecular weights offrom about 7,000 to about 100,000 with the preferred range being fromabout 12,000 to about 50,000. These compounds, while particularly usefulas partitioning phases in the higher temperature range of 350-to 650 C.may also be used at any of the lower temperatures wherein VPC is carriedout. Additionally, the siloxy carboranyl phase material of thisinvention may be useful at temperatures greater than 650 C. since notall the phase material will volatilize off at 650 C. For example, athermogram (TGA similar to FIG. 2) run on the siloxycarboranyl phase attemperatures up to l,000 C. still showed significant quantities of thephase material that we not volatilized off.

The siloxy carboranyl material'ot this invention is generally preparedfor use in chromatographic analyses by dissolving in a suitable solventsuch as ethers, ketones, aromatic hydrocarbons and other substitutedhydrocarbons as exemplified by diethyl ether, methylene chloride, methylethyl ketone, chlorobenzene, bromobenzene, aniline, xylene, N-methylpyrolidone, decaline, etc. The liquid phase is then deposited onto asolid support material which is packed into a column. The inert solidsupport material is generally made from diatomaceous earth such as isavailable commercially under the name Chromosorb W (Johns-Manville).However, any inert support material may be used providing it is capableof withstanding the temperature at which the VPC will be carried out.

FIGS. 1-4 are graphic evaluations of the temperature stability ofdifferent liquid phases.

The problem of running'the chromatograph column at a temperature isillustrated in FIG. 1 wherein comparisons of a heated column containingmethyl silicon gum (SE-30) as the partitioning phase with another columncontaining the siloxy carboranyl phase of this invention is made. A 15percent by weight siloxy carborane of the formula:

was placed on a Chromosorb-W support and run on a F and M ScientificModel 700 chromatographic instrument in a similar manner as a methylsilicone column. The temperature was programmed from to 460 C. at 20 C.per minute. As noted in FIG. I, a point is reached where the detectorsbegin to respond as if material was being chromatographed. Actually,what is happening is that the phase is being volatilized off the supportand being carried to the detector. The temperature at which this beginsto occur becomes the upper operating limit. As can be seen from thefigure, methyl silicon begins to volatize off at about 350 C. while thecarborane based partitioning phase of this invention goes beyond 500 C.with no volatilization being detected.

Another evaluation of the temperature stability of difierent phases isshown in FIG. 2. This figure shows the results of a Thermal GravimetricAnalysis (TGA) using methyl silicone gum (SE-30), 25 percent cyanoethylsilicone (General Electric XE-30) and the siloxy carborane of thisinvention (same material as used in FIG. 1) as phase sample material.Basically in TGA a small sample of material is heated in a selectedatmosphere and the change in weight recorded as a function of Jiltemperature. As noted earlier, when a VPC phase material is heated in acolumn, a point is reached where it loses weight (volatilize and hence,a direct similarity is seen between TGA and the action of temperature onthe VPC column.

The results noted in FIG. 2, show the cyanoethyl silicon beginning tovolatilize at about 225 C., the methyl silicon at about 350 C. and thesiloxyl carboranyl phase of this invention at about 625 C. These resultsshow the siloxy carboranyl phase at nearly 300 C. higher than theindustry standard, methyl silicon.

The following examples are illustrative of this invention.

EXAMPLE I Initially a packed column containing the partitioning phasewas prepared by dissolving 1.55 grams of siloxy carboranyl material ofthe formula:

L (in. 511* (Ell I having molecular weight of about 20,000 in a solventmethylene chloride. An 8.5 gram sample of inert carrier materialChromosorb-W DMCS (80-100 mesh) was wet with the same solvent and thenmixed with the carborane solution. The solution with the inert supportmaterial was then placed into a flat enamel pan on a steel plate withoccasional stirring, the solvent was evaporated oil into a hood draft.The support material holding the partitioning phase was then packed intoa 5.5 foot length by %-inch O.D. stainless steel tubing. This tube wasthen placed in a gas chromatographic instrument (F and M ScientificModel 700) which was equipped with thermal conductivity detectors.

A solution consisting of the distillation residue of a commercialaromatic amine mixture (containing various isomers of toluene diamine)was dissolved in methanol to make up a ercent by weight solution. A 3microliter portion of this solution was injected using a hypodermicsyringe into the previously prepared column containing the supports withthe siloxy carboranyl phase held thereon. Helium was used as an inertcarrier gas and was injected at a flow rate of 40 cc. per minute with aninjection port temperature of 420 C. An oven temperature was programmedat a rate of 20 C. per minute starting at 200C.

The chromtographic analysis of this sample is shown in FIG. 3 along witha comparative analysis performed using a methyl silicon phase under thesame operating conditions. As noted, the siloxy carboranyl phase of thisinvention showed residual components in the 450 to 500 C. range whereasthe methyl silicone phase showed no residual components after about 300C.

EXAMPLE II A packed column was prepared in a manner similar to thatdescribed in Example I except that the siloxy carboranyl material usedhad the formula In order to decrease further polymerization of the phasein the column, 200 microliters of N,O-Bis-(trimethylsilyl)-acetamidewere injected onto the column in 50 microliter portions at about 50 C.increments from ambient temperature to 200 C. A 10 percent by weightsample mixture comprising halogenated alcohols, epoxides, and telomersresulting from the reaction thereof was made and analysis performed inthe same manner as Example I.

The results are shown in FIG. 4 along with a comparative analysisperformed using a methyl silicone phase (SE40). As noted, using thesiloxy carboranyl phase, several residual components were shown from 300to about 500 C. whereas the methyl silicone phase showed no residualcomponents after about 300 C.

EXAMPLE H] A packed column containing the partitioning phase wasprepared by dissolving 1.55 grams of siloxy carboranyl material of theformula:

having molecular weight of about 17,000 in a solvent diethyl either. An8.5 gram sample of inert carrier material, Chromosorb-W-DMCS (-100 mesh)was wet with the same solvent and then mixed with the carboranesolution. The column packing was then prepared in a manner similar tothat described in Example I. This material was packed into a 5.5 footlength by %-il1Ch O.D. stainless steel tubing. The column was placed ina gas chromatographic instrument (F and M Scientific Model 700) equippedwith flame ionization detectors. The column was conditioned at 400 C.for 24 hours and then temperature programmed from to 500 C. at 10C./minute.

A 30 percent solution (by volume) consisting of a mixture of fiveandsix-ring polyphenyl ethers in toluene was then chromatographed byinjecting l microliter of the solution into the instrument whilemaintaining the column oven at 360 C. The chromatogram for this sampleindicated that toluene eluted within 15 seconds, three isomers of thefive-ring material eluted after between 2.5 and 3.5 minutes and thesix-ring material eluted after from 8.75 to l0.5 minutes.

What is claimed is:

l. in a method of performing a vapor phase chromatographic analysis on avolatile sample material wherein a liquid partitioning phase is used,the improvement comprising using as said partitioning phase a materialhaving recurring structural units of the formula:

where each R and R substituent is independently selected from the groupconsisting of alkyl of from one to eight carbon atoms and aryl of up to10 carbon atoms, x is l to 5 and said material has a molecular weight offrom about 7,000 to about 100,000.

2. The method of claim 1, where x is l.

3. The method of claim 2, where each R is CH; and each R is phenyl.

4. The method of claim 1, where x is 2.

5. The method of claim 4, where each R and R is CH;

6. The method of claim 1, wherein x is 3.

7. The method of claim 6, wherein said partitioning phase material hasrecurring structural units of the formula:

sexes It It

2. The method of claim 1, where x is
 1. 3. The method of claim 2, whereeach R is CH3 and each R'' is phenyl.
 4. The method of claim 1, where xis
 2. 5. The method of claim 4, where each R and R'' is CH3 .
 6. Themethod of claim 1, wherein x is
 3. 7. The method of claim 6, whereinsaid partitioning phase material has recurring structural units of theformula:
 8. The method of claim 1, wherein said material has a molecularweight of from about 12,000 to about 50,000.